1. Field of the Invention
The present invention relates to a loading device of a leg extension machine, in particular to a loading device using the linear proportion between current and torque of a DC or brushless motor and a pair of gear disks as resistance components to improve traditional exercise loads.
2. Description of the Related Art
Various different types of fitness equipments are designed according to different fitness exercises. For instance, a treadmill machine is designed specially for jogging or running, and a leg extension machine is designed specially for training abductor and adductor (inner and outer thigh muscles) and leg and foot muscles, and these machines were disclosed in U.S. Pat. Nos. 7,396,319, 5,575,744 and 4,478,411.
In addition to leg extension components, the main structure of a conventional leg extension fitness machine further includes a resistance device as disclosed in U.S. Pat. No. 7,396,319 and shown in FIGS. 1 and 2 for providing an exercise load. The fitness machines of this sort include extension elements 12 installed at the front of a seat 11 and provided for exercising a thigh 121 and a calf 122, a movement and internal or external direction switching component 13 installed at the bottom of the fitness machine, a resistance arrangement 14 disposed at a lateral side of the fitness machine and linked with the movement and internal or external direction switching component 13 by a cable 15 to provide a load. When the exerciser's thigh and calf drive the extension element 12 to move inward or outward to link the movement switching component 13, the resistance component 14 still provides an exercise load to the exerciser.
However, most conventional exercise loads are resistance components 14 composed of a plurality of weight stacks 141, but such conventional loads still have the following drawbacks:
1. The weight stack 141 comes with a large volume and occupies much space. If an exerciser needs to adjust the exercise load by increasing the number and the weight of the load such as the weight stack 141, it will take much time and effort for the exerciser to make the adjustment, and the exerciser also has to stop the exercise to do so, and thus it is difficult to achieve the expected exercising effect.
2. The load such as the weight stack 141 is heavy and cannot be adjusted easily. Furthermore, a variable load for continuous and smooth exercise cannot be achieved according to a curve, and thus the exercising effect will be lowered, and there is also a potential risk of an exercise-induced muscular injury.
3. If the load such as the weight stack 141 is lifted by a transmission cable 15 and then released slowly, an annoying sound will be produced, and the irritating sound will cause discomfort to the exerciser. Furthermore, the transmission cable 15 is operated together with a winch, and it makes the machine more complicated.
In addition to the aforementioned three drawbacks, the loading device of the conventional leg extension fitness machine 10 still requires a manual mechanism to switch exercises for training the exerciser's inner thigh and outer thigh. Obviously, the prior art requires further improvements.